Medical electrode construction

ABSTRACT

There is disclosed an electrode construction of the type including a terminal arrangement and support structure for said terminal arrangement, said support structure adapted for the transcutaneous application of the electrode to a patient. The support structure may be fabricated from a layer of foam or microporous material, or plural layer employing a combination of both, or from a layer of conductive adhesive. The terminal arrangement may be of single terminal or multi-terminal design, and is provided by a conductive pattern printed on a semi-flexible plastic-like sheet, wherein said pattern is printed with a conductive ink of the type employing a conductive metal, such as silver, in a binder composition. The disclosure also contemplates novel structure for connection of the electrode to a lead wire, as well as several novel, overall designs for the construction of the electrode support means.

This application is a division of application Ser. No. 100,904, filedDec. 6, 1979, now U.S. Pat. No. 4,365,634.

BACKGROUND OF THE INVENTION

The present invention relates to electrodes, and more particularly todisposable medical electrodes of the type employed in the transcutaneousmonitoring of biological or physiological electrical potentialassociated with muscular activity.

In recent years, medical science has developed the art of transcutaneousmonitoring to a rather high degree and for a variety of purposes. Thistype of monitoring is used to detect muscular activity of the heartmuscle by use of electrical apparatus referred to in the art as anelectrocardiograph (ECG). The resulting traces or electrocardiogramsachieved with this procedure provide a diagnostic tool which enables thecardiologist to detect heart disease and general defects, etc. Inaddition to cardiomuscular applications, transcutaneous monitoring canbe employed to indicate the degree of nerve blockage resulting due toanesthetization of a patient during surgery. In this regard, one set ofelectrodes are used to apply a controlled, low voltage potential to aparticular muscle nerve, and a second set of electrodes may be used tomonitor the resulting muscular contractions. These contractions arerecorded on a electromyograph (EMG), with the resulting trace indicatingthe degree of effectiveness being achieved with the anesthetic.

The electrodes initially developed for ECG or EMG applications werereusable, and referred to as "permanent electrodes". These electrodeswere of a type which utilized a non-conductive base that was applied tothe skin either by means of suction cups or straps, with a metalterminal element housed within the non-conductive base and connected tothe ECG or EMG apparatus via lead wires. To assure proper electricalcontact, an electrolytic gel or paste was often employed in conjunctionwith the metal terminal. In many of these early designs, the terminalsemployed were either pure silver, German silver (pewter) orsilver-plated metals or plastics, as it was found that silver providedsuperior results due to its tendency not to store an electrical charge.As can be appreciated, these permanent electrodes were rather expensiveto manufacture. Also, the permanent type of electrode required that itbe cleaned and disinfected after each use and before reuse. Thisprocedure was time consuming such that disposable or single useelectrodes were soon developed which out of necessity had to be of aninexpensive construction. Examples of several types of disposableelectrodes can be found in U.S. Pat. Nos. 3,989,035 and 3,805,769.

These disposable electrodes typically included a support structure forthe metal terminal element in the form of a relatively thin adhesivelycoated layer or disc of cellular foam, or in some applications, a thinmicroporous tape is used. The requisite metal terminal was provided bythe employment of a two piece snap fastener engaged either directlythrough the foam or tape layer, or in some instances, the supportarrangement was apertured with a second layer of impervious materialoverlying the aperture, and the snap fastener carried by said secondlayer. In conjunction with the snap fastener, a porous matrix wasapplied which in the case of a pregelled electrode, was impregnated witha quantity of gel, and a cover arrangement of some sort placed over boththe gelled matrix and the adhesively coated surface of the supportarrangement.

The snap fasteners which provide the electrical terminals for theseprior art electrodes have proven to be both expensive, and a sourcecontributing to inconsistent performance of the electrode. In thisregard, the snap fastener component associated with the gelled matrix isof a two part construction, with an inner element and an outer element,and is either totally or partially constructed of silver, stainlesssteel, nickel, or a silver-coated plastic or metal component. As such,the snap fastener is a relatively expensive component of the overallelectrode construction, however, this design is tolerated as the snapfasteners lend themselves to the high speed automated construction ofthe electrode, necessary to achieve low cost production.

Further, it has been found that in use the snap fastener contributessignificantly to the often erratic performance of the electrode. In thisregard, the electrode is connected to the ECG apparatus by means of alead wire having a female type snap connector on the end thereof engagedover the post or male component of the snap fastener. This connectionprovides considerable mass with respect to the remainder of electrode,such that patient movement results in alterations in the disposition ofthe electrode terminal with respect to the skin of the patient. Morespecifically, any movement producing tension in the lead wires wouldtend to pull the electrode terminal away from the patient's skin,whereas if the patient should happen to roll over, the protruding natureof the snap fastener would cause the metal terminal to be forcedinwardly toward the skin, all of which contributing to the production ofrather inconsistent ECG traces. As a further problem, electrodes withprojecting snap fastener type terminal means do not lend themselves tostacking, and must be handled carefully during shipping and storage. Inthis regard, any rough handling or compressing together of theelectrodes will tend to squeeze the gel from the gelled matrix.

The electrode system and electrode design of the present invention, asillustrated and described hereinafter, eliminates the need for the snapfastener as a component of the terminal means. Further, the presentdesign achieves elimination of the snap fastener component, in a mannerwhich results in improved performance, in that stability of the terminalposition vis-a-vis the patient's skin is attained. Still further, thisimproved electrode design lends itself readily to automated assembly,and is usable with an overall system that envisions further improvementsin the manner of connecting the electrode to the lead wire extendingfrom the ECG or EMG apparatus.

More specifically, the electrode designs of the present inventionutilizes a terminal arrangement provided by a pattern printed withconductive ink on a sheet of stable, semi-flexible, plastic-likematerial. The term "semi-flexible" is used with respect to the terminalbearing sheet for purposes of description, in that said sheet must becapable of slight flexure, yet must be relatively stiff or rigid, so asto resist any stretching or permanent deformation during use. Shouldstretching or deformation occur, this would result in fracture orinterruption in the continuity of the printed conductive pattern, andthereby destroy its effectiveness as a conductive element. It has beenfound, that a relatively thin, clear, plastic-like film such as thatsold under the trade name "MYLAR", is satisfactory for this purpose.

Looking to the overall basic construction, the electrode design of thepresent invention utilizes a support arrangement or layer which may befabricated from a relatively thick, closed cell foam material of varioustypes widely known in the trade, with one side of the foam support layercoated with a standard medical grade adhesive for securing or adheringthe electrode to the skin of the patient. The support layer is aperturedand the semi-flexible plastic-like terminal bearing sheet is affixed tothe side of the support layer opposite that upon which the adhesive isapplied. In this regard, the plastic-like sheet is positioned with theside having the conductive ink pattern thereon facing the support layer,with the terminal portion of said conductive ink pattern aligned withthe associated aperture. Preferably, the conductive ink pattern alsoincludes a conductor portion extending away from the area of theaperture, to which a lead wire is connected. The aperture in the supportlayer and the overlying plastic-like sheet material serve to define awell or chamber in which is disposed a porous or reticulated matrix,such as may be provided by a sponge-like plastic-like material, manyversions of which are well known in the art. The porous matrix, or "gelpad" as it is often termed, is impregnated with a quantity ofelectrolytic gel, also of known formulation. A suitable easily removablecover arrangement overlies the adhesive coating on the support layer andthe gel pad to prevent deterioration of the gel during storage.

The use of the semi-flexible terminal bearing sheet provides arelatively low mass terminal arrangement, which in use achieves aconstant, stable positioning of the terminal means with respect to theskin of the patient. That is to say, the terminal portion will be spacedfrom the patient's skin, with the intermediate space filled by theelectrolyte gel and the gel impregnated pad or matrix. This spacing isreferred to in the art, and hereinafter, as the "gel column". Morespecifically, due to the low mass of the terminal arrangement providedby the conductive pattern on the sheet and the manner of connection ofthe electrode to the ECG apparatus, any patient motion, rolling over ofthe patient, or any tension on the ECG lead wires will not affect gelcolumn stability to a great extent. Thus, the present design provides aninexpensive, disposable electrode capable of attainment of a consistent,highly accurate trace from the ECG apparatus.

As mentioned above, the manner of connecting the electrode to the ECGapparatus lead wire as contemplated by the present invention is also ofsignificance, and contributes to the overall effectiveness of theelectrode system. In both the single terminal and multi-terminal designsillustrated and to be discussed, the lead wires are connected at areasremote from the terminal portion. In one preferred, disclosed embodimentthe plastic-like, semi-flexible terminal bearing sheet includes a tabsegment which is free of connection or adherence to the underlyingsupport layer. The conductive pattern printed on said semi-flexibleplastic-like sheet includes a conductor portion extending along this tabsegment, such that the tab may be inserted within an electricalconnector affixed to the end of an ECG lead wire. As will be discussed,the construction of the connector and the tab segment are such that theyserve to isolate any stress or strain from the area of the terminalportion, which might affect the gel column.

A further aspect of the present invention and one most particularlyapplicable with respect to the single terminal electrode designdiscussed above, is the manner by which the design lends itself toautomated fabrication. In and of itself, automated fabrication of anelectrode is not novel, one such method of being illustrated anddescribed in the aforementioned U.S. Pat. No. 3,805,769. The presentinvention, however, contemplates a novel method of assembly that isparticularly advantageous with respect to the single terminal design asdisclosed herein and other existing or possible future electrodedesigns.

In addition to the single terminal type of construction discussed above,the invention also contemplates various forms of multi-terminalassemblies, one of which is illustrated in the drawings and discussed indetail hereinafter. With the illustrated, contemplated design, aplastic-like, semi-flexible terminal bearing sheet is employed to jointogether two similar shaped support layers, each having one or moreapertures therein with a terminal element on said sheet aligned witheach aperture. With this arrangement, the semi-flexible sheet not onlycarries the terminal means, but acts as a hinge or connection betweenthe respective support layer to provide an integral yet articulatedassemblage. As will become apparent from the discussion to follow, thisdesign is extremely advantageous with regard to both use of themulti-terminal assembly, its manufacture, and packaging thereof.

The present invention is possessed of numerous features and advantages,in addition to those discussed specifically above. It is believed thatthese features and advantages will become apparent from the detaileddescription of the invention which follows, taken in conjunction withthe accompanying drawings which form a part of said description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a single terminal electrode,including the cover member;

FIG. 2 is an assembled view of the electrode of FIG. 1, with a lead wireconnector attached to the electrode assemblage;

FIG. 3 is a plan view of the semi-flexible, plastic-like terminalbearing sheet, with the adhesive layer applied thereto;

FIG. 4 is an exploded sectional view of the electrode of FIG. 3;

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 3;

FIG. 6 is a partial sectional view of one form of connector arrangementto be employed with the electrode assemblage of FIGS. 1 and 2 and theelectrode tab segment engaged therewith;

FIG. 7 is a longitudinal sectional view of the connector of FIG. 6 withthe tab portion of the electrode disengaged;

FIG. 8 is a partial sectional view of an alternate form of connector tothat as shown in FIG. 6;

FIG. 9 is a longitudinal, partial sectional view of the connector formof FIG. 8, with the tab segment of the electrode disengaged;

FIG. 10 is an exploded perspective of an alternate form of electrodeassemblage constructed in accordance with the invention;

FIG. 11 is an exploded sectional view of the electrode as illustrated inFIG. 10;

FIG. 12 is a sectional view of the electrode embodiment in FIG. 10adhered to the skin of a patient;

FIG. 13 is a schematic, diagrammatic view illustrating the respectivesteps of a method of constructing the electrode assemblage of FIGS. 1-5;

FIG. 14 is a partial schematic view illustrating several of the steps inthe method of assembly as illustrated in FIG. 13;

FIG. 15 is a plan view of a multi-terminal electrode, constructed inaccordance with the present invention, with an upper foam layer removedfrom the left hand portion of the assemblage, as viewed;

FIG. 16 is a view of the adhesively coated surface of the electrode ofFIG. 15, illustrating the reverse side of said electrode and theapplication of a deactivating compound to certain portions of saidadhesively coated surface;

FIG. 17 is a partial sectional view of the connector portion of theelectrode of FIG. 15, taken along the lines 17--17 of said FIG. 15;

FIG. 18 is a partial sectional view through one of the terminal portionsand the gel pad of the electrode assemblage of FIG. 15 taken along theline 18--18;

FIG. 19 is a partial, exploded view of the electrode construction asillustrated in FIG. 15;

FIG. 20 is a partial plan view of an extension portion on thesemi-flexible plastic sheet at which a terminal portion of theconductive ink pattern is shown;

FIG. 21 is a perspective view of the manner in which the electrodeassemblage of FIG. 15 is prepared for packaging;

FIG. 22 is a perspective view illustrating the electrode assemblage inthe pre-packaged construction;

FIG. 23 is a sectional view taken along the line 23--23 of FIG. 22;

FIG. 24 is an exploded perspective view of still another type or form ofelectrode design in accordance with the invention;

FIG. 25 is a sectional view along the line 25--25 of FIG. 24;

FIG. 26 is a perspective view similar to FIG. 24, and illustrating analternate form of connection of the electrode to a lead wire;

FIG. 27 is a sectional view taken through a completed electrode of FIG.26, generally along the line 26--26;

FIG. 28 is a plan view of a multi-terminal electrode constructed inaccordance with the design of FIG. 24, and having pre-attached leadwires; and

FIG. 29 is a sectional view taken along the line 29--29 of FIG. 28, andillustrating the crimp-type connection for the lead wires.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is possessed of numerous aspects, and fourdistinct but related embodiments of electrode constructions areillustrated in the drawings. The first embodiment is encompassed byFIGS. 1-9, and relates to a single terminal electrode assemblagedesignated generally 30 which is employed with a lead wire and connectorassembly 32 and utilizes the relatively thick, foam type supportarrangement or layer. FIGS. 10-12 illustrate an alternate form of asingle terminal design 80 which is adapted for use with the assembly 32(not shown in said figures). This alternate design 80 employs a supportarrangement which is comprised of a relatively thick foam ring toprovide the desired gel column, and a thinner, more extensivemicroporous layer, which microporous layer includes the adhesivematerial employed to affix the electrode to the skin of a patient. InFIG. 13 and 14 there is shown rather schemtically, a method ofassemblage for the electrode construction 30 of FIGS. 1-5. Amulti-terminal electrode construction in accordance with the presentinvention is shown in FIGS. 15-23, and designated generally 120. Still afurther type of electrode construction is shown in FIGS. 24-29, whereinthe support arrangement is provided by a conductive adhesive layer,thereby enabling elimination of the foam and/or microporous layers aswell as the porous matrix. In the discussion that follows, even thoughcommon components of the various embodiments will be designated bysimilar terms, for purposes of description and understanding differentreference characters will be utilized. As a further matter, sincecertain of the features of the various electrode designs are embodied inextremely thin layers or components, certain of these have beenexaggerated dimensionally in the drawings in order to facilitatedescription and discussion.

Looking now to FIGS. 1-5, the construction of a single terminalelectrode assemblage 30 is shown and will be considered in detail. Inthis regard, the term "electrode construction" is used collectively toindicate the assemblage as actually applied to the skin of a patient, aswell as said assemblage in conjunction with a release liner type cover34. More specifically, the electrode construction 30 includes a base orsupport arrangement 36 in the form of a layer of foam-like plasticmaterial such as polyethylene foam which material is preferably of anon-reticulated or closed cellular construction to prevent absorption ofthe gel material. The base or support layer 36 includes a generallycentral aperture 38 extending completely through the layer 36. Onesurface of the support arrangement provided by the foam layer 36includes a coating 40 of an adhesive material (FIGS. 4 and 5), whichadhesive material may be any of a number of commercially availablemedical grade adhesives presently in use with prior art types ofelectrodes, and thereby well known in the art.

Affixed to the surface of the support layer 36 approximate saidadhesively coated surface is a sheet of semi-flexible plastic-likematerial 42 which is secured in overlying relation with respect to theaperture 38 by means of an extremely thin ring-like component or layer43 having adhesively coated surfaces 45 and 47 on opposite sidesthereof; said component being termed hereinafter "a double sidedadhesively coated annulus". The assemblage of the sheet of plastic-likematerial 42 to the support layer 36 in effect closes one end of theaperture 38 and serves to cooperate therewith to define a well orchamber 38' for a purpose to be discussed. The sheet 42 is referred toas constructed of a "semi-flexible, plastic-like material" for purposesof description and general definition. In this regard, it is to beunderstood that there exists numerous types of materials from which thesheet 42 can be constructed; these materials, however, must possesscertain properties in that it is important that they be relatively thinand slightly flexible, yet they must not be subject to stretching orpermanent deformation during normal use or during assembly. A materialwhich has proven satisfactory for use in construction of the sheet 42 isa clear plastic material sold in sheet form under the trademark "MYLAR".

Further, the semi-flexible, plastic-like sheet 42 has terminal meansthereon in the form of a conductive ink pattern 44 printed directly onone surface of said sheet. Due to the clear nature of the preferredmaterial for the semi-flexible sheet 42, this pattern is visible fromthe opposite surface of said sheet. The pattern 44 of the disclosedembodiment 30 includes a generally circular terminal portion 46 and aconductor portion 48. As can best be seen in FIG. 1, the conductorportion 48 extends from the terminal portion 46 along a tab segment 50of said sheet 42, which tab segment includes a pair of notches 52 forthe purpose to be discussed.

Disposed in the well 38' is a porous matrix or gel pad 54, preferablyformed of an open cellular sponge like plastic material. Keeping in mindthe fact that the electrode 30 is of the pregelled type, there is alsoincluded a quantity of electrolytic gel (no reference character), whichimpregnates the matrix 54 and effectively fills the well 38' provided bythe aperture 38. This electrolytic gel can be any of variouscommercially available products, as for example sodium chloride in agar.In the event that the electrode is not to be pregelled, the employmentof said electrolytic gel may be dispensed with, without variation in theoverall construction.

With reference to FIGS. 3, 4 and 5, it should be noted that the doublesided adhesive annulus 43 includes an aperture 56 which is smaller indiameter than the aperture 38 in foam layer 36, and upon assembly,surrounds the terminal portion 46 without overlying said terminalportion, FIG. 3. As such, when the semi-flexible sheet 42 is mounted tothe support arrangement, 36, a portion 47a of the adhesive coating 47 onsaid ring 43 is exposed interiorly of the aperture 38, as best seen inFIG. 3. Thus, upon disposition of the gel matrix 54 in the aperture 38,as shown in FIG. 5, said matrix 54 is adhered to the semi-flexibleplastic-like sheet 42 by means of the exposed adhesive portion 47a.

To complete the electrode construction 30, the cover 34 is applied tothe adhesively coated surface 40 of the foam layer 36, said cover 34overlying said surface 40, as well as the gelled matrix 54. The cover 34is preferably constructed of a high density polyethylene having arelease coating on the surface thereof engaged against the adhesivelycoated surface 40 of the foam layer 36. As such, when it is desired toutilize the electrode, the cover 34 can be removed easily and theelectrode construction applied to the skin of the patient, with theadhesive surface 40 providing the means for affixing and maintaining theelectrode in proper position.

Returning to the semi-flexible sheet 42 with the conductive ink pattern42 thereon, the ink utilized is applied by conventional printingtechniques in an extremely thin layer, 0.001-0.010". As such, patternsother than the pattern 44 as specifically illustrated may be easilyemployed. Ink of the general type contemplated is comprised of acomposition of a conductive metal, carried within a binder. It ispreferred that the ink utilized employ silver as the conductivecomponent. Ink of this nature can be obtained from numerous sources, onesuch source being E. I. DuPont DeNemours and Company. The particularcompositions available from this company include silver in a proprietarybinder system specifically designed to adhere to a plastic-like materialsuch as "MYLAR" without peeling or cracking during flexure of saidmaterial. As such, it can be appreciated that the material used for theplastic-like sheet or substrate 42 must be sufficiently rigid to resistany stretching or deformation during normal use or assembly. Shouldstretching occur, the danger exists that the ink pattern will befractured, destroying its continuity and the ability of said conductivepattern 44 to function as an electrical terminal arrangement. As anadditional matter it is also preferred that the surface of the terminalportion 46 of said conductive silver ink pattern be chlorided to producea thin silver chloride coating, which has proven to provide superiorperformance. This process of chloriding can be accomplished in any oneof several known manners, such as electrodeposition or by reaction withchlorine gas.

An additional feature of the invention that should be noted, is theconstruction of the sheet 42 with its tab portion 50, and the locationof the adhesively coated annulus 43 thereon, as best seen in FIG. 3. Inthis regard, the sheet 42 is fabricated and the conductive ink pattern44 is printed thereon prior to application of the adhesive annulus 43.The adhesive annulus 43 includes an aperture 56, such that upon itsapplication to a surface of the semi-flexible sheet 42, it willencompass the terminal portion 46 of the conductive ink pattern 44, butpreferably does not cover or overlie said terminal portion 46. As shownin FIG. 3, the adhesively coated annulus extends only to the generalperiphery of the main segment of the sheet 42, and does not extend alongthe tab segment 50, thus overlying only partially the conductor portion48. When the sheet 42 is assembled to the support layer 36 only the mainsegment thereof is adhered to the upper surface of said support layer36, the tab segment 50 remaining free and unsecured thereto. In additionto providing the surface 47a to which the porous matrix 54 is attached,and securing the sheet 42 to the support layer 36, the annulus 43 alsoserves to seal the gel matrix chamber 38' and prevent migration orleakage of the gel along the tab segment 50. As such, taking intoaccount the non-porous nature of the foam layer 36, the sheet 42 and therelease liner 34, it can be seen that there is provided a substantiallyhermetically sealed chamber 38' for the gel which serves to resistdeterioration and drying out of the gel during storage prior to use.

The free or unsecured nature of the tab segment 50 enables the electrodeto be connected to ECG apparatus by means of a lead wire arrangement 32having an electrical connector 60. As seen in FIGS. 2 and 5, the tabsegment 50 is engaged with or received within the electrical connector60 and a connection is made with the conductor portion 48 on said tabsegment 50. Details of two preferred or anticipated designs forconnectors 60 are illustrated in FIGS. 6-9 and will be discussed morefully hereinafter. While these specific designs are believed to be novelper se, it is also believed that the general concept utilizing a freetab segment and a printed ink conductor segment thereon to achieveelectrical connection with the lead wire arrangement 32 is a novelconcept.

Looking to FIGS. 6 and 7, there is illustrated a first form or type ofelectrode connector 60 which may be employed in the electrode system ofthe present invention. The connector 60 includes a housing 62 having anopen end 63 leading to the interior thereof, wherein there is mounted aspring-type clip terminal 64 having upper and lower arms 65 and 66,respectively. A lead wire 68 passes inwardly of the housing with thehousing being crimped to engage said lead wire at 69, said wire 68 beingconnected to the terminal 64. At the forward entry portion of the openend of the housing 62 there is provided a pair of spaced, ramp shapedprojections 70. The projections 70 are sized and spaced apart such thatupon disposition of the tab segment 50 within the housing, theprojections 70 will be received within the notches 52 of said tabsegment. The tab segment 50 is received between the spring-like arms 65and 66 with the upper spring arm 65 forcing the tab segment downwardlyto maintain the tab segment engaged over the projections 70.Accordingly, if any tension is applied to the lead wire 68, theengagement of the projections 70 in the notches 52 will serve to resistinadvertent disconnection, and also function to achieve a degree ofstrain relief, isolating any stress from the area of the electrodeterminal portion 46. It can be appreciated further, the metal terminal64 is designed to engage the printed ink conductor portion 48 on the tabsegment 50, thereby effecting an electrical connection. Further, sincesaid metal terminal 64 includes a pair of opposed arms 65 and 66,inverting of the connector 60 upon assembly would not precludeattainment of a proper electrical connection.

FIGS. 8 and 9 illustrate a modified type of connector 60' for use with atab segment 50 having an aperture 72 formed thereon. In this regard, theconnector housing 62' has a projection or post 74 formed thereon, andsized for dispostion in said aperture 72. Accordingly, in the assembledor engaged position, as shown in FIG. 8, the spring terminal 64' willengage the printed ink conductor portion 48 to effect the desiredelectrical connection, and also maintain the tab segment 50 engaged overthe post 74.

A modified form of electrode construction in accordance with the presentinvention is illustrated in FIGS. 10-12, and designated generally 80.The electrode embodiment 80 differs from the electrode construction 30in that the support arrangement includes a relatively thick ring 82which may be made of a foam material or a rigid plastic, and a sectionof microporous tape material 84 having an adhesive coating 86 on onesurface thereof for adhering the electrode to the skin of a patient. Thering 82 includes a central aperture 83, while the section of microporoustape 84 has an aperture 85 of a somewhat smaller dimension, for apurpose to be discussed more fully hereinafter. In certain applicationswhere an electrode will be in place for an extended period of time, useof a microporous tape layer prevents dermatalogical problems as itallows air to reach the patient's skin surface. Suitable types ofmedical grade of microporous tape are available and well known in theart, one being sold under the trade name "MICROPORE" by the 3M Company,and another by Johnson & Johnson under the trademark "DERMICIL".

The remaining construction of the electrode 80 is somewhat similar tothat of the electrode 30 discussed above, in that the terminalarrangement is provided by a semi-flexible plastic-like sheet 42 ofidentical construction to that previously detailed, said sheet includinga tab portion 50, a pattern 44 printed thereon with the conductive inkand defining a terminal portion 46 and a conductor portion 48. Adouble-sided adhesive annulus 43 is used to affix the semi-flexiblesheet 42 to the upper surface of the ring 82, with the tab 50 remainingfree of any connection thereto. The lower surface of the ring 82 asmentioned previously, includes an adhesive layer 86, which affixes thering 82 to the upper surface of the micro-porous disc 84. Theapplication of the semi-flexible plastic-like sheet 42 to the ring 82serves to define a well 83' in which a porous matrix 54 is disposed. Aswas the case with the electrode 30, the double-sided adhesive annulus 43has a central aperture somewhat smaller than the aperture 83 of thering, such that a portion of the adhesive will be exposed with theporous matrix 54 secured thereto. A cover member 34 is provided, havingan upper surface 34' upon which there is provided a release linercoating which enables the cover 34 to be removed easily immediatelyprior to application of the electrode to the skin of a patient.

In FIG. 12, the assembled electrode construction 80 is shown mounted tothe skin 90 of a patient. It can be seen that the relatively thick ring82 serves to provide a substantial well 83' for the gel pad 54, whichalso defines the height of the gel column. Further, it should be notedthat the aperture 85 in the micro-porous support arrangement component84 is of slightly smaller dimension than the gel matrix 54, so as tooverlap slightly said matrix in the assembled condition. Thisoverlapping design serves to further retain the gel matrix 54 inposition, and prevent migration of the gel along the interface with thepatient's skin 90.

Attention is now invited to FIGS. 13 and 14, wherein a preferred methodof manufacture of the electrode construction 30 is shown, theillustration therein depicting the successive steps of said methods insomewhat schematic fashion. Initially, an elongate strip 100 of foammaterial 36 in roll form is provided, with said strip 100 having a firstrelease liner 102 covering the adhesive surfaces 40 thereon. The stripmaterial 100 is oriented for feeding to a first station I with therelease liner 102 facing upwardly. At the station I the apertures 38 areformed in the strip 100 by a die or punch 104 at spaced successivelocations along the strip. At a separate sub-station II, thedouble-sided adhesively coated annulus or ring 43 is applied to thesheet of semi-flexible plastic-like material 42, to attain apreassembled component as was illustrated and discussed with respect toFIG. 3. Prior to the application of the annulus 43, to the semi-flexiblesheet 42, the printed ink conductor pattern 44 is applied to a sectionof plastic-like sheet material by a conventional printing process (notshown) and the sheet material die cut or otherwise formed to the desiredshape for the sheet 42.

Next, the preassembled terminal bearing sheet 42 and adhesive annulus 43are affixed to the undersurface of the strip 100 at station III. Withreference to FIG. 14, the resulting assembly is illustrated in the lefthand portion of said FIG. 14, as viewed, which illustrates the lowersurface of the strip 100 at station III. In this regard, it can be seenthat the semi-flexible clear sheet 42 is positioned such that theterminal portion 46 of the conductive pattern 44 is aligned with theaperture 38. Looking now to the central portion of FIG. 14, the strip100 has been rotated 180°, such that the upper surface carrying thefirst release liner 102 is the facing surface. It can be seen that aportion 47a of the adhesive annulus 43 extends inwardly of the aperture38 and is disposed in surrounding relationship to the terminal portion46.

This is the condition of the partially assembled electrode construction,as it is presented to station IV.

At station IV, a precut porous matrix 54 is supplied and disposed withinthe aperture 38, this results in the matrix adhering to the adhesiveportion of 47a. This step is also illustrated in the central portion ofFIG. 14.

The strip 100 next passes to the station V, wherein a quantity ofelectrolytic gel is injected into said matrix, which gel impregnates thematrix 54 and fills the well 38'. In this regard, a dispenser 106 willmeter out a pre-determined quantity of the gel to prevent over fillingof the gel chamber.

The strip 100 then passes to station VI, at which the apertured, firstrelease liner 102 is removed and discarded as waste. As can be seen, theapertured release liner 102 is coiled for easy disposition, asillustrated 108. The strip 100 with the partially assembled electrodethereon next passes to the station VII, at which a second release liner34 is applied. The second release liner 34 is preferably a high densitypolyethylene sheet with a release liner coating 34' thereon, whichmaterial ultimately forms the cover for the pregelled electrode 30. Inthis regard, the second release liner material 34 is in roll form 110,and is applied to the strip 100 by a roller 112.

As the strip 100 passes from the station VII, the basic construction forthe electrode 30 is complete. At station VIII, a die cutter or punch 114severs the completed electrode construction 30 from the strip 100. Theremaining portion of the strip 100 thus becomes waste and can be easilydiscarded, as the adhesively coated surfaces thereon remains covered bythe waste portion of the release liner 34.

Looking to FIGS. 15-23, there is illustrated a multi-terminal electrode,designated generally 120, and constructed in accordance with the presentinvention. Multi-terminal electrode constructions of this nature areoften referred to in the art as "back pads", in that they are affixed tothe patient's back to provide monitoring during chest or abdominalsurgery and during recovery thereafter, wherein it would be impracticalto utilize chest mounted electrodes. Accordingly, while themulti-terminal electrode illustrated is of the "back pad" type, it is tobe kept in mind that other types of multi-terminal electrodes such asused in muscle stimulation, electromyographic monitoring or pain therapymay also be constructed in accordance with this invention; as such withrespect to multi-terminal designs, the embodiment of FIG. 15 to bediscussed is merely illustrative of one preferred type, and theinvention is not limited thereto.

Looking now to FIGS. 15 and 19, the multi-terminal electrodeconstruction 120 contemplates employment of a preconnected lead wirearrangement 122, including a plurality of separate lead wires 123. Afurther point to be kept in mind for better understanding of thediscussion to follow, is that the electrode 120 as shown in FIG. 15 hasa sheet-like component or layer removed from the left-hand portion asviewed for purposes of illustration.

More specifically, the electrode 122 is comprised of a supportarrangement provided by a pair of similarly shaped sections ofrelatively thick foam material 124. As was the case with the previouslydiscussed electrodes, employment of a closed cellular type foam ispreferred, however, any one of a number of various commerciallyavailable foam materials may be utilized.

Each section of foam material 124 includes a pair of spaced apertures126 formed therein. A singular section or sheet of semi-flexible,plastic-like material 128 is provided, said sheet being mounted to eachof the foam sections 124 and in effect interconnecting said sections 124by bridging the space or joint therebetween. The semi-flexible sheet 128is preferably constructed of a plastic-like material of the same type asdiscussed with respect to electrodes 30 and 80, that is the term being"semi-flexible" being used to designate a type of material, such as"MYLAR", which will flex slightly, but will not stretch or permanentlydeform during normal use, assembly or storage. Said semi-flexibleplastic-like sheet 128 which will be discussed in greater detailhereinafter, is initially affixed to the foam sections 124 by a partialadhesive coating on the upper surfaces of the foam sections 124 in theareas 130, as indicated. To complete mounting of the sheet 128, a secondrelatively thin foam layer or sheet 132 is employed which has anadhesive coating on the under surface thereof. Upon assembly of saidsecond sheet 132, as illustrated in the right hand portion of FIG. 15,said sheet 132 overlies the semi-flexible plastic-like sheet 128 and issecured to both said sheet 128 and the upper surface of the foam layer124 by said adhesive coating. It should be noted that while it ispreferred that the layer or sheet 132 be of a foam or cellular material,other suitable materials may be employed.

The specific construction of the semi-flexible, plastic-like section orsheet 128 will now be considered. In this regard, the sheet 128 will bediscussed primarily with the left hand portion of FIG. 15 and FIG. 19,it being understood that the right hand portion of said sheet isessentially identical, being a mirror image of that as illustrated.Further, with regard to FIG. 19, which is an exploded view of theelectrode construction 120, the left hand portion of said sheet 128 canbe viewed in somewhat greater detail.

The sheet 128 includes a plurality of arm sections or extensions 136eminating from a base or central section 150, each of which terminatesis generally circular portion 138. Each of the respective circularportions 138 includes an aperture 140 formed therein, as is bestillustrated in FIG. 20. A plurality of individual terminal meanscorresponding in number to the apertures 126 in the sheet 124 areprovided on the semi-flexible sheet 128. The terminal means in thepreferred form of the invention are provided by four individual patterns144, printed on the underside of the semi-flexible sheet 128 with aconductive ink of the same general type and in the same manner asdiscussed previously. Each pattern 144 includes a terminal portion 146and an elongate conductor portion 148. As best shown in FIG. 20, theterminal portion 146 of the illustrated embodiment is of a ring-likeconfiguration, encircling the aperture 140, with the conductor portion148 extending along the arm or extension 136. The respective conductorportions 148 on each half of the sheet 136 extend in oppositedirections, and terminate adjacent to each other on the base or centralsegment 150 of said sheet. The lead wire arrangement 122 is affixed tothe base segment 150 and electrical contact with the conductor portions148 is attained in a manner which will be discussed more fullyhereinafter with respect to FIG. 17.

Completing the basic electrode construction 120 are a plurality ofporous matrix members 154 which are engaged in the apertures 126, asbest shown in FIG. 18. With reference to said FIG. 18 and also FIG. 15,it should be noted that the circular end portion 138 on the respectiveextensions 136 are of a diameter slightly less than that of the openings126. Accordingly, when the semi-flexible plastic-like sheet 128 ismounted in position as shown in FIG. 15, the circular end segments 138overlie the apertures 126 only partially. Further, taking into accountthe presence of the opening 140 in said circular end portions 138, itcan be appreciated that when the second, relatively thin sheet of foammaterial 132 is applied over the semi-flexible plastic-like sheet 128,portions of the adhesive coating on said sheet 138 remained exposed,interiorly of the aperture 126. Thus, upon disposition of the matrix 154with the aperture 126, said matrix will be adhered to the exposedadhesive portions, as is shown in FIG. 18. Thus, the respective matrixesare maintained in operative association with the terminal portions 146carried on the circular end segments 138 of the projection 136.

Directing attention to FIG. 17, the manner of connecting the lead wirearrangement 122 to the semi-flexible plastic-like sheet 128 isillustrated. In this regard, a suitable crimp-type terminal connector162 is included on the ends of the individual lead wires 123, thecrimp-type terminal being engaged through the upper surface of thesemi-flexible plastic-like sheet 120 at location 160, and bent over toeffect firm electrical contact with the conductor portion 148 on theunder surface of said sheet. The relatively thin foam like sheet 132 isengaged over the terminal connections 162, and is adhered in firmengagement to the plastic-like sheet about the area of said terminalconnection 162, such that the engagement of said sheet with the terminalconnection and its associated lead wire 123 serve to provide a measureof strained relief. As such any tension applied to the lead wires 123will be taken up, at least partially, by the engagement of the flexiblesheet 132 with the lead wire 123.

In FIG. 16, the under surface of the electrode 120 is shown with saidelectrode in the fully open condition. In this regard, the under surfaceof the respective support layers or sheets 124 is coated with aconventional medical grade adhesive for attachment of the electrode tothe skin of the patient. Since the extent of the adhesive on the undersurface is rather large, and further since it is not always desirablenor necessary to have the entire surface area of the electrode inadhesive contact with a patient's skin, a portion of adhesive isdeactivated to avoid dermatological problems which may occur afterextended periods of use of the electrode or back pad 120. In thisregard, a medical grade silicone coating, as designated generally 164,is applied to the central area of each of support arrangement 124, asindicated. This coating in effect deactivates the adhesive in saidcentral area, with the adhesive on the remaining portion, the areassurrounding the apertures 126 and gel pads 154, remain active andcapable of effecting attachment of the electrode.

As was mentioned previously, the support arrangement for the preferreddesign utilizes a pair of separate, similarly shaped sheet sections 124,maintained in assembly by their joint connection to the plastic likesheet 128. This arrangement is for a specific purpose which will bediscussed; however, it should be kept in mind that the present inventionalso envisions use of but a single support arrangement wherein therespective halves are provided by a single layer or sheet of foammaterial. The purpose for use of the arrangement wherein thesemi-flexible plastic-like sheet 128 interconnects the respective layers124 is to attain flexibility. More specifically, it can be appreciatedthat these back pads are rather extensive. Accordingly, with thedisclosed arrangement, the central portion 150 of the plastic-like sheet128 provides a hinge which permits the respective halves of theelectrode to flex and adjust to the contour of the patient's back. Also,as will be apparent in conjunction with the discussion to follow withregard to FIGS. 21-23, this flexibility facilitates packaging of theelectrode 120.

Looking first to FIG. 21, the manner for packaging or completing theelectrode arrangement for storage is shown. As mentioned above, thesemi-flexible plastic-like sheet 128 provides a hinge between therespective foam sections 124 of the support arrangement. This hingearea, the central segment 150 of the sheet 128, does not includeportions of the conductive pattern 144 providing the terminal means.Accordingly, the respective foam layers 124 may be folded over uponthemselves, as is indicated in FIG. 21, without undue flexing of thepattern 144. In this regard, a sheet of release liner material 168 isdisposed intermediate the respective halves of the electrode, said sheet168 having a release coating on both sides thereof. As such, therespective halves or sections 124 of the electrode are releasablysecured against said sheet 168 in overlapped relation, as is bestillustrated in FIGS. 22 and 23, with the lead wire arrangement 122coiled as illustrated. As such, there is provided a compact arrangementfor packaging and storage purposes.

In FIGS. 24-29, a still further modified version of the presentinvention is illustrated. In FIGS. 24-27 there is shown two forms of asingle terminal electrode construction, designated 170 and 170'respectively. In FIGS. 28 and 29, there is shown a multi-terminalelectrode construction using the general concept as to be discussed withrespect to the single terminal electrodes 170 and 170'.

Looking first to FIGS. 24 and 25, the electrode 170 differs from theelectrode 30, previously discussed, primarily in that the foam layer 36and the gelled matrix 54 have been replaced by a specially constructedconductive adhesive layer 171. More specifically, the electrode 170 ofFIG. 24 is illustrated in exploded fashion with the assembledarrangement being shown in FIG. 25, affixed to a patient. The electrode170 is comprised of a sheet of semi-flexible plastic-like material 172upon which is printed a conductive pattern 174. The pattern 174preferably is formed with a silver ink, or some other type of conductiveink printed directly on the sheet material as discussed previously, andsaid pattern 144 includes a terminal portion 176, and a conductorportion 178. The semi-flexible plastic-like sheet 172 also includes thetab segment 180 adapted to be received within a connector 182 affixed tothe end of a lead wire 184 in a manner similar to that as discussed withrespect to the electrode of FIGS. 1-5. It should be noted that theconductor portion 178 extends along the length of the tab 180, which inturn extends from the periphery of the main segment of the electrode,which conductor portion 178 will be associated in electrical contactwith a metal terminal housed within the connector 182.

The layer of conductive adhesive is affixed to the major or main segment173 of the semi-flexible plastic-like sheet 172, but does not extendalong the tab 180, whereby said tab remains free for engagement within aconnector 182. A cover member 190, having a release liner coated surface191 is provided, which is releasably attached to the under surface ofthe adhesive layer 171, and can be peeled off or removed for mounting ofthe electrode to the skin 90 of a patient, as is shown in FIG. 25.

Due to the conductive properties of the adhesive layer 171, the gel pador matrix and foam support layer used with the electrodes discussedpreviously, are not required. As such, the conductive adhesive layer 171is not apertured, as was the adhesive annulus 43 discussed previously,and overlies the terminal portion 176.

The adhesive layer 171 may be provided by any one of several knownelectrically conductive adhesives. One such conductive adhesive isproduced by Johnson & Johnson Company under the trade name "BIO-HESIVE",and is disclosed in U.S. Pat. No. 4,066,078, which in turn references apending U.S. application Ser. No. 509,207, filed Sept. 25, 1974 andentitled "Hydrophilic Random Interpolymer Compositions and Method forMaking Same". Other conductive adhesives and methods for renderingadhesive materials conductive are known in the art; as for example inU.S. Pat. Nos. 4,008,721; 3,998,215; 3,993,049; and 3,911,906. Theaforesaid patents disclosed that certain adhesive compositions may berendered conductive by a number of methods, including the dispersing ofconductive materials such as conductive salts or metals throughout thecomposition. The adhesive layer 171 of the present invention ispreferably constructed of a hydrophilic adhesive compositionmanufactured by Tyndale-Plain-Hunter, Ltd., which material may berendered conductive by any one of the above noted methods, or othermethods known in the art. This hydrophilic material is disclosed fullyin U.S. Pat. Nos. 3,822,238; 4,156,066; and 4,156,067. Basically, theadhesive layer 171 is of a double sided nature so that it has onesurface secured to the semi-flexible plastic-like sheet 172 and anopposed surface for attachment to the skin of a patient.

It can be appreciated that the elimination of the foam layer and the gelpad not only reduces the material costs, but also simplifies the methodof production of the electrode.

A second or modified version of the electrode 170 is illustrated inFIGS. 26 and 27, said modified design being designated 170'. In thisregard, the electrode 170' includes a semi-flexible plastic-like sheet172' with terminal means formed thereon preferably in the form of aprinted ink conductive pattern 174' having a terminal portion 176' and aconductor portion 178'. In place of the tab segment 180 which extendsfrom the periphery of the main portion 173 of the semi-flexibleplastic-like sheet 172 of the electrode 170, shown in FIG. 24, theembodiment of FIGS. 26 and 27 utilizes a tab 180' in the form of acut-out depending from the main segment 173' of said sheet. The tabsegment extends upwardly from said main segment 173' of the sheet 172'for attachment to a connector 182', as shown.

The electrode 170' also utilizes the conductive adhesive layer 171', asdiscussed previously. In order to prevent adherence of the tab 180' tothe double-sided adhesive layer 171', the tab 180 is coated with amedical grade of silicone or the like, during manufacture. Accordingly,upon application of the conductive adhesive layer 171', said tab 180'remains free of adhesion thereto, and can be lifted up out of the planeof the main segment 173' of a flexible sheet 172' for attachment to theconductor. Therefore, except for the manner of forming the tab 180', theelectrode 170' is essentially identical to that as discussed with regardto FIGS. 24 and 25.

Turning now to FIGS. 28 and 29, there is illustrated a multi-terminalelectrode constructed in accordance with the concept of the invention asillustrated in FIGS. 24-27, said electrode being designated generally192. The electrode 190 is of the type having a lead wire assembly 193pre-attached thereto. Further, the electrode 190 includes a single sheetof semi-flexible plastic-like sheet material 194 having separateindividual conductive patterns, 195 printed thereon. Each pattern 195includes a terminal portion 196, and a conductor portion 198. Theconductor portions 198 on each half of the semi-flexible plastic-likesheet extend in opposite directions toward each other, and terminateproximate a central segment of the sheet. At this location, a crimp-typeterminal 197 connector carried on the end of each lead wire of theassembly 193 is engaged through the upper surface of the semi-flexibleplastic-like sheet 194 and disposed in electrical contact with theconductor portion 198, of the conductive pattern 195 on the undersurfaces of said semi-flexible plastic-like sheet 194. This connectionbeing best shown in FIG. 29, which is a sectional view showing theelectrode 192 engaged to the skin 90 of a patient.

As was the case with the electrode 170 and 170', the electrode 192includes a layer of conductive adhesive 199; FIG. 29 on the undersurface of sheet 194. In practice, it is undesirable to have a junctionof dissimilar metals such as the copper which may be used for theterminal connection 197 and the silver or silver chloride coating on theconductor portion 198 in association with the conductive adhesive 199,as there exists the danger of electrolytic corrosion. Therefore, thejoint or connection of the terminal 197 with the conductor portion 198is hermatically sealed by placement of a quantity of epoxy or wax, orsome other substance, designated generally 200, over the point ofconnection on the under side of the sheet 194. The conductive adhesivelayer 199 is then applied in overlying relation to the undersurface ofthe electrode, preferably over the entire electrode. If desired, saidadhesive may be subject to zoned application, in whatever patterndesired, provided the terminal portions 196 of the conductive pattern195 is covered.

While the drawings disclose and the preceding specification discussesvarious preferred embodiments of the invention, it is not the intent tolimit said invention thereto. In this regard, it is contemplated thatthose skilled in the art and possessed of the present disclosure maydevelop various alternative forms of the invention, without departingfrom the spirit and scope of said invention, as defined in the appendedclaims.

The invention is claimed as follows:
 1. In combination, a disposablemedical electrode and a conductor element in the form of a lead wirehaving a connector assembly on one end thereof, said electrodeincluding; a support arrangement having an adhesive coating on at leastone surface portion thereof for attachment of the electrode to the skinof a patient; a terminal member affixed to the other surface portion ofsaid support arrangement in the form of a plastic-like semi-flexiblesheet, said sheet having a first, terminal carrying segment of an areaconsiderably less than that of the support arrangement surface portionto which it is attached such that the periphery of said first segment isdisposed inwardly of the periphery of said support arrangement, and anelongate tab segment extending from said first, terminal carryingsegment and terminating within the periphery of said supportarrangement; a conductive pattern formed on said terminal memberincluding a terminal portion on said first segment and a conductiveportion in association with said terminal portion and extending alongsaid tab segment; an annular coating of adhesive on said first, terminalcarrying segment attaching said terminal member to the supportarrangement, said annular adhesive coating surrounding said terminalportion, and said adhesive coating overlying said conductive portioninwardly of the tab segment thereby to prevent the migration of moisturealong said conductive portion, said annular adhesive coating terminatingwithin the periphery of said first, terminal carrying segment therebyleaving said tab segment free of attachment to said support arrangementfor engagement thereof with said connector assembly; said tab segmentfurther including at least one aperture formed therein; said lead wireconnector assembly including a housing, a metal terminal member disposedwithin said housing, and a protuberance formed on said housing andengaged with said aperture in said tab segment, such that upon assembly,said tab segment is disposed in said housing, with said metal terminalmember in engagement with the conductive portion on said tab segment,and said connector assembly protuberance is engaged in said aperture ofthe tab segment to prevent inadvertent disconnection of said connectorassembly and said electrode.
 2. The combination as recited in claim 1,wherein said aperture in said tab segment, comprises a pair of cutoutsalong opposite edges of said tab segment, and said protuberance formedon said connector assembly housing comprises a pair of spacedprojections disposed in said cutouts.
 3. The combination as recited inclaim 1, wherein said aperture on said tab segment comprises an openingformed in said tab segment, and said protuberance on said housingcomprises a post disposed in said opening.
 4. The combination as recitedin claim 1, wherein said metal terminal member comprises a spring-liketerminal member which will grip said tab segment to enhance theelectrical contact between said metal terminal member and the conductiveportion.
 5. The combination as recited in claim 1, 2, 3 or 4, whereinsaid terminal member is provided by a thin layer of conductive inkprinted on a first surface of said semi-flexible plastic-like sheet,which conductive ink defines a pattern including the conductive portionextending along said tab segment of said sheet, and the terminal portionon the first segment of said semi-flexible plastic-like sheet affixeddirectly to said support arrangement.
 6. A disposable medical electrodeof the type adapted for connection to a conductor element in the form ofa lead wire having a connector assembly on one end thereof, saidelectrode including; a support arrangement having an adhesive coating onat least one surface portion thereof for attachment of the electrode tothe skin of a patient; a terminal member affixed to the other surfaceportion of said support arrangement in the form of a plastic-likesemi-flexible sheet, having a first terminal carrying segment of an areaconsiderably less than that of the support arrangement surface portionto which it is attached such that the periphery of said first segment isdisposed inwardly of and terminates within the periphery of said supportarrangement, and an elongate tab segment extending from said first,terminal carrying segment and terminating within the periphery of saidsupport arrangement; a conductive pattern formed on said terminal memberincluding a terminal portion on said first segment and a conductiveportion in association with said terminal portion and extending alongsaid tab segment; an annular coating of adhesive on said first, terminalcarrying segment attaching said terminal member to the supportarrangement, said annular adhesive coating surrounding said terminalportion and overlying said conductive portion inwardly of the tabsegment thereby to prevent the migration of moisture along saidconductive portion, said annular adhesive terminating within theperiphery of said first, terminal carrying segment thereby leaving saidtab segment free of attachment to said support arrangement forengagement thereof with said connector assembly.
 7. A disposable medicalelectrode according to claim 6, wherein said tab segment includes atleast one aperture for engagement with a mating projection on aconnector assembly.
 8. A disposable electrode as recited in claim 7,wherein said aperture in said tab segment, comprises a pair of cutoutsalong opposite edges of said tab segment.
 9. A disposable electrode asrecited in claim 7, wherein said aperture on said tab segment comprisesan opening formed in said tab segment.
 10. A disposable electrodeaccording to claim 6, wherein said support arrangement includes anaperture, said semi-flexible plastic-like sheet overlying said aperturewith said terminal portion aligned with said aperture, and a porousmatrix disposed in said aperture.
 11. A disposable electrode as recitedin claim 6 or 10 wherein said terminal portion is provided by a thinlayer of conductive ink printed on a first surface of said semi-flexibleplastic sheet, which conductive ink defines a pattern including theconductive portion extending along said tab segment of said sheet, andthe terminal portion on the first segment of said semi-flexibleplastic-like sheet affixed directly to said support arrangement.